Medical Research>> Research Projects on the System of K-Channels>> Subcutaneous migration of radioactive isotopes

SUBCUTANEOUS MIGRATION OF RADIOACTIVE ISOTOPES

Title.

Study of migration pathways of hypodermically injected Tc-99m.

Background.

Radioactive isotopes are substances that emit radioactivity. When they are injected into the human body, they are transported or captured by different organs. A camera capable of detecting the radioactivity shows their distribution and accumulations.

It had been described that the subcutaneous injection of a specific radioactive isotope (known as 99mTc and injected in the chemical form of sodium pertechetate) in points of least electrical resistance prompts the progressive and rapid longitudinal migration of the tracer following a specific and constant track, both in human and in animal experiments. From 1960, it has been known that acupuncture "points" have a lower electric resistance than the skin around them, and the migration pathway of the sodium pertechetate coincided with acupuncture's "meridian transmission lines".

It was not known whether that migration always occurred whenever any radioactive substance was injected. Nor had methodologically reliable studies been made to demonstrate whether this migration was produced only when the substance was injected in points of lower electrical resistance or also when it was injected in points of the skin with normal electric resistance.

Finally, the migration observed may be explained by the lymphatic or vascular drainage of the area in which the substance had been injected.

Objectives.

1. To determine whether longitudinal migration occurs after the subcutaneous injection of any radioactive isotope or whether it is specific to sodium pertechetate.

2. To determine whether it occurs after the subcutaneous injection in any point or only in the areas of least electrical resistance.

3. To gather reliable data showing whether the migration is due or not to the transport of the isotope through the veins, nerves or lymphatic vessels.

Methodology.

16 male Beagle dogs between 18 and 36 months old were anesthetized and were injected with radioactive isotopes of sodium pertechetate (99mTc), sodium iodide (131I), thallium chloride (201Tl) and rhenium sulfide. This last is transported through the lymphatic vessels and serves to visualize them. Only one experiment was made in each animal.

All of the isotopes were injected in two different points situated on the back of the animal's paw at least 5 cm. between each. The "control" point was a place that has the same electric resistance as "normal" skin. As an example of normal skin, that of the ear was used, since there are no acupuncture points on the ear and its electric resistance is similar to that of the rest of the skin. The "study" point was a place that had lower electrical resistance than that of the ear skin.

In different experiments, the different kinds of radioactive isotopes were injected in the study and control points. Additionally, sodium pertechetate was injected into the vein underlying the study point in the last series of experiments and sodium pertechetate and thallium, in the same needle, was injected in a study point.

Participants, along with the Science Department of the Foundation.

Departments of Nuclear Medicine of the Hospital Clínico of Barcelona, Morphological Sciences at the Central University of Barcelona (Medical School), and Animal Surgery at the Autonomous University of Barcelona (Veterinary School).

Funded entirely by the Kovacs Foundation.

Results.

Published in the Journal of Nuclear Medicine (Kovacs FM, Gotzens V, García A, et al. Experimental study on radioactive pathways of hypodermically injected technetium-99m. J Nucl Med 1992; 33:403-7).

To summarize, they indicate that:

1. No radioactive isotope was observed to migrate when it was injected into points of normal electric resistance. Nor was any migration observed when injecting isotopes other than sodium pertechetate in points of least electric resistance.

2. Each time sodium pertechetate was injected into points of least electric resistance, its migration was observed constantly, approximately at 2.5 cms per minute and always following the same longitudinal pathway.

3. The characteristics of the migration rule out the possibility that the radioactive isotope was carried through the nerves, vessels or lymphatic system. For example, when it was injected in a vein underlying the point of least electrical resistance, transport of a different speed and pathway was observed. Additionally on injecting sodium pertechetate and thallium at the same time, it was observed that the first was transported while the second was not.

In conclusion, these results show that 99mTc in the form of sodium pertechetate is transported subcutaneously by a previously unknown corporal mechanism.